Heat sealing moistureproofing coatings



Patented Nov. 11, 1947 HEAT SEALING MOISTUREPROOFING COATINGS James A.Mitchell, Kenmore, N. Y., assignor to E. I. du Pont de Nemours &Company, Wilmington, Del., a corporation of Delaware No Drawing.Application February 14, 1942, Serial No. 430,885

4 Claims. 1

This invention relates to moisture-resistant sheet wrapping material,especially moistureproofed transparent non-fibrous sheet. Moreparticularly it appertains to age-resistant heat scalablemoistureprooflng coatings on films of regenerated cellulose and thelike,

One of the newer sheet wrapping materials consists of a thin cellulosicbase sheet having a moistureproofing coating. The manufacture of typicalbase sheet (film, foil, pellicle, skin, tissue, web) is described in U.S. A. Patents 1,548,864 (Brandenberger), and 2,123,883 (Ellsworth).Representative coating compositions and the ap- Dlication thereof areset out in U. S. A. Patents 1,737,187 (Charch and Prindle), 1,826.697-8(Charch and, Craigue), 2,042,589 (Charch and Hershberger), 2,147,180(Ubben), 2,159,151 (Hershberger), 2,169,366 (Meigs) and 2,201,747(Staudt).

The coating is usually a continuous, unbroken layer comprisingessentially moistureprooflng material (material which does not dissolvemore than an infinitesimal amount of, if any water), for example, a waxy(wax-like) substance such as parafiin wax, and a cementing (binding,flimforming) material therefor, for example, cellulose nitrate.

To improve the properties, inter alia, flexibility, of the coating,plasticizing material, for example dibutyl phthalate, is generallyincorporated therein. The base sheet as produced usually containssoftening material, for example glycerol. and has, therefore, adequatepliabllity.

To overcome any haziness which might result from some proportions andcombinations of other components ofthe coating, transparentizing(blending, homogenizing) material, for example, resins and gums such asDamar and ester gum, is ordinarily included.

The present state of the moistureproofing art, to which reference ismade for conventional details in the interest of brevity, is indicatedby U. S. A. Patents Nos. 1826,696 (Charch and Prindle), 1,962,338(Charch), 1,972,869 (Charch, Hyden and Siemann), 1,989,681 (Charch),1,990,080 (Leach and Siemann), 1,997,583 (Hitt), 1,997,857 (Charch),2,022,490 (Charch) 2,030,962 (Charch, Hyden and Siemann), 2,042.638(Slemann), 2,061,374 (Charch) 2,064,292 (Charch), 2,065,792 (Charch),2,077,396 (Charch andHershberger),

2,077,399 (Collins and Larson), 2,077,400 (Collibs), 2,079,379(Mitchell), 2,079,395 (Bradshaw), 2,085,816 (Meigs) 2,087,013 (Bateman),2,094,771 (Charch and Hershberger), 2,096,122 (Maney), 2,098,534-542(Charch, Brubaker and Meigs), 2,100,377 (Brubaker), 2,122,418 (Gladdingand Maney), 2,122,433 (Meigs), 2,137,636 (Barrett), 2,144,383 (Melgs),2,147,623 (Charch), 2,147,629 (Charch), 2,159,007 (Charch and Bateman)2,177,645 (Flint and Mitchell), 2,192,314 (Izard and Mitchell),2,193.831 (Mitchell), 2,205,210 (Latour), 2,205,428 (Mitchell),2,209,965 (Finzel), 2,213.252 (Mitchell), 2,216,812 (Flint), and2,234,565 (Lanning).

In spite of the many desirable properties of ordinary moistureprooftransparent regenerated cellulose film, its usefulness in some fields,for example, where heat sealing is required, is severely circumscribed.Sealing package wrappers by means oiheat and pressure is one of thecommonest and simplest methods known and employed, and it will beobvious, therefore, that a wrapping material not capable of being sosealed is at a considerable disadvantage. Extensive research has beenand is being carried out, with the object of improving the heat sealingcharacteristics of moistureproof transparent sheet.

Holt (U. S. A. patent application Serial No. 302,323, filed November 1,1939) has proposed that iratol (a hard brittle resin-like materialhaving a. reddish-black color en masse, made by treating beta naphtholwith rubber) be employed as the cementing agent in this type of coatingin order to produce better heat seals. The seals are initially verygood, but they weaken rapidly. Deterioration of the heat seal issometimes so complete that the package wrapper loosens and moisturegains access to the package contents through the section of the wrapperembodying the seal. In addition, the coating dlscolors rapidly,particularly when subjected to sunlight or heat, to such an extent thatpackages embodying the same are not commercially acceptable. This lastis a reasonable objection because discoloration of the wrapper suggeststo the consumer that foodstuffs and related materials so wrapped are notin the best of condition.

' It has now been found that color formation in moistureproofingcoatings employing iratol as the cementing agent, can be restrained(avoided, pre- 3 vented, inhibited, curbed, repressed, obviated), andthe products embodying the same stabilized and their life very greatlylengthened, by incorpo.. rating therein (compounding with, dilutingwith) N:N:N' :N-tetra-ethyl- 4:4'-di-amino-di-phenyl methane and similarsubstances. These substances are comprehended by the general structuralformula:

(ARI), A u in which b, d, p and q are numerals from the group consistingof 0, 1 and 2, and .1: and y are numerals from the group consisting oland 1.

The primary object of this invention was to provide improvedmoistureproofing and moisturereslsting coatings for Cellophane(regenerated cellulose). Other Objects were to improve heat sealablemoistureprooflng coatings, to lengthen the life or heat scalablecoatings containing lratol. to stabilize iratol against deteriorationfrom age, to prevent the formation of color in moistureproofing coatingsand the like containin iratol, and to devise heat sealing processes andcompositions which would give heat seals having a lon life. A generaladvance in the art, and other ob- Jects which will appear hereinafter,are also contemplated.

How the foregoing objects and related ends are accomplished will beapparent from the following exposition, in which are disclosed theprinciple and divers embodiments of the invention, including the bestmode contemplated for carrying out the same. Parts are given by weightthroughout the application unless otherwise specified.

Comparative heat seal strengths appear to be the most satisfactory wayof showing the effectiveness (stabilizing efiect) of the diaminodiphenyl methanes in lratol. A standard heat seal strength test (U. S.A. Patent No. 2,147,180 to Ubben) was used to secure the data in theexamples which follow. In this test two strips of the coated material(in this case regenerated cellulose sheeting) 1.5 inches wide aresuperimposed one on the other so that opposite faces of the material arein contact. A seal is made across the width of the material at one endby placing the material on a metal plate heated to 130 C., and rollingthereover a roller inch wide weighted to 650 grams. The two strips sosealed are separated at the end where they are unsealed and placed in astretching device such as a Suter testing machine. By gripping the freeends of the strips in suitable clamps, one of which is fixed while theother is moved away at a constant speed of 12 inches per minute, andmeasuring the force applied, the desired data is obtained. The force ingrams required to pull the sheets apart is taken as a measure of theheat seal bond strength.

Example I N- 0 HI) 4-H ale Prepare a moistureprooflng coatingcomposition by dissolving a mixture of 90 parts iratol (Example X of U.S, A. Patent 2,158,530 type), parts paraffln wax (M. P. 60 C.) and 2parts of NzNzN' :N'-tetraethyl 4:4 diamino diphenyl methane insufficient toluene to give a 12% solids dispersion. Pass a sheet orregenerated cellulose approximately 0.00088 of an inch thick throughthis lacquer. Remove the solution in excess of that required to leave oneach side a coat 0.0005 inch thick. from the surface by means of doctorExample II Apply a moistureproofing coating consisting of Parts Iratol(Ex. X, U. S. A. P. 2,158,530)

Paraffin wax (M. P. 60 C.) 10 N:N:N' :N'-tetramethyl 4:4 diaminodiphenyl methane 2 to a regenerated cellulose sheet in the mannerdescribed in Example I. The product so produced will be highlytransparent, moistureproof, and exhibit the same initial heat seal valueas the composition of Example 1. Aging at C. will reduce the heat sealvalue to 150 in three weeks.

Example III Ap ly a moistureproofing coating consisting of:

Parts Iratol (Ex. X, U. S. A. P. 2,158,530) 90 Paralfin wax (M. P. 60C.) 10 4:4'-diamino diphenyl methane 2 to a regenerated cellulose sheetin the manner described in Example I. The product so produced will behighly transparent and moistureproof. It will have an initial heat sealof 250 which will. upon aging at 95 0.. drop to 150 in two weeks andremains at that value for over four weeks more.

Example IV Apply a moistureproofing coating consisting of:

Parts Iratol (Ex. X, U. S. A. P. 2,158,530) 90 Paraflin wax (M. P. 60C.) 10 4:4-diamino diphenyl methane 3 to a regenerated cellulose sheetin the manner described in Example I. The product so produced will behighly transparent, moistureproof, and exhibit good heat sealcharacteristics.

Example V Apply a moistureproofing coating consisting of Parts Iratol(Ex. X, U. S. A. P. 2,158,530) 90 Paraffin wax (M. P. 60 C.) 10

N:N'-dimethyl-N:N' diethyl 4:4 diamino diphenyl methane 2' to aregenerated cellulose sheet in the manner described in Example I. Theproduct so produced will be highly transparent, moistureproot, andexhibit a good initial heat seal of 250 which will, upon aging at 95 0.,drop slowly to in four weeks, and hold that value for at least two morewee s.

Eaiample VI Apply a moistureproofing coating consisting of Parts Iratol(Ex. X, U. S. A. P. 2,158,530) 90 Parailin wax (M. P, 60 C.) 104:4'-diamino diphenyl 3 to a. regenerated cellulose sheet in the mannerdescribed in Example I. The product so produced will be highlytransparent and moistureproot. It will have an initial heat seal valueof 300 which will. upon aging at 95 C., drop only to 140 in four weeks.

- NzNzN'zN' tetramethyl 4:4 diamino diphenyl methane 3 to a regeneratedcellulose sheet in the manner de scribed in Example I. The product soproduced will be highly transparent, moistureproof, and exhibit goodheat seal characteristics.

Example VIII Apply a moistureprooflng coating consisting of Parts Iratol(Ex. X, U. S. A. P. 2,158,530) 90 Paraffin wax (M. P, 60 C.) N:N:N':N'tetraethyl 4:4 diamino diphenyl methane 3 to a regenerated cellulosesheet in the manner described in Example I. The product so produced willbe highly transparent, moistureproof, and exhibit good heat seal.

Example IX Apply a moistureprooflng coating consisting of Parts Iratol(Ex. X, U. S. A. P. 2,158,530) 90 Paraflin wax (M. P, 60 C.) 10Tetramethyl diamino benzhydrol 2 to a sheet of regenerated cellulose inthe manner described in Exam le I. The product produced in this mannerwill be highly transparent, moistureproof, and exhibit an initial heatseal of 250, which during aging at 95 C. drops only to 130 in six weeks.

Example X Apply a moistureproofing coating consisting of:

. Parts Iratol (Ex. X, U. S. A. P. 2,158,530) 90 Parafiln Wax (M. P, 60C.) l0 N:N:N':N' tetraethyl 4:4 diamino diphenyl methane 10 to a.regenerated cellulose sheet in the manner described in Example I. Theproduct so produced will be highly transparent, moistureproof, and

to a regenerated cellulose sheet in the manner described in Example I.The product so produced will be highly transparent, moistureprooi, andexhibit good heat seal.

Example XII Apply a moistureproofing coating consisting of:

. Parts Iratol (Ex. X, U. S. A. P. 2,158,530) 90 Paraflln wax (M. P. 60C.) 10

4:4-diamino-diphenyl ether 3 to a sheet of regenerated cellulose in themanner described in Example I. The resultant product will be highlytransparent, moistureproot, and exhibit good heat seal.

Example XIII Apply a moistureprooflng coating consisting of:

Parts Iratol (Ex. X, U. S. A. P. 2,158,530) Paraflin wax (M. P. 60 C.)10 2:4 diamino diphenyl amine 3 to a sheet of regenerated cellulose inthe manner described in Example I. The resultant product will be highlytransparent, moistureproo! and exhibit good heat seal.

Example XIV Apply a moistureproofing coating consisting 01':

Parts Iratol (Ex. X, U. 8. A. P. 2,158,530) 90 Paraflln wax (M. P. 60C.) 10 4:4'-diamino-benzophenone 3 to a sheet of regenerated cellulosein the manner described in Example I. The resultant product will behighly transparent, moistureproot, and exhibit good heat seal.

Example XV Apply a moistureprooflng coating consisting 01':

Parts Iratol (Ex. X, U. S. A. P. 2,158,530) 90 Paramn wax (M. P. 60 C.)10 Di(p-ethoxyphenylaminc) ethane 2 to a sheet of regenerated cellulosein the manner described in Example I. The product .produced in thismanner will be highly transparent, moistureproof, and exhibit good heatseal.

Preferably the addition materials are from the group consisting of N:N:N':N-tetraethyl-4:4- diamino diphenyl methane, NtNtN :N'-tetramethyl4:4'-diamino-diphenyl-methane, N:N'- dimethyl-N:N'-diethyl-4:4'-diaminodi henylmethane, 4:4'-diamino-diphenyl-methane, 4:4- diamino-diphenyl, N:N N :N'-tetramethyl-4 4 diamino-diphenyl, N:N:N':N'-tetraethy1-4:4'-diamino-diphenyl, N:N'-dimethyl NzN' diethyl- 4z4'diamino diphenyl, N:N-dimethy1-4:4'-diamino-diphenyl, N N-dimethyl-44'-diamino-diphenyl methane, N N-diethyl-4 4'-diamino-diphenyl methane,tetramethyl-diamino-benzl'iydrol, di (p-ethoxyphenylamino) -ethane,4:4'-diamino benzophenone, 2:4 diamino diphenylamine,4:4'-diamino-diphenyl ether, 4:4'-diamlno-diphenyl-ethane, N: N N:N'-tetramethyl- 4:4 diamino diphenyl ethane, 3:3-diaminobenzophenone,N:N:N' :N' tetraethyl 4:4'-diamino diphenyl ethane,tetramethyl-diaminobenzophenone, tetraethyl-diamino-benzophenone,tetramethyi benzidine, 4:4 tetrarnethyl diamino-triphenyl-methane, N N-dimethyl-N N'- diethy] 4:4'-diamino-diphenyl-ethane,4:4'-diamino-diphenyl-amine, N:N' tetramethyl-4z4'-diamino-diphenyl-amine, and NzN-tetramethyl- 4 4 -diamlno-diphenylether.

Iratol is obtained when rubber is worked on a. rubber mill (or relatedapparatus such as a Banbury mixer) with about 5% to 55% of its weight ofbeta naphthol (or similar monohydric phenol which contains nosubstituents other than halogen and hydrocarbon radicals) in thepresence of a small amount of a special catalyst, for example,dihydroxy-fluoroboric acid or sulfuric acid, for about 15 minutes at C.The material is quite unlike rubber and the heretofore known rubberderivatives, as will be apparent from a consideration of its chemicaland physical properties. The new material being denser, sinks whenplaced in water, will not adhere to rubber, is more soluble inhydrocarbon solvents than cyclized rubber (J. I. E. C. XXXIII, 389), andwhen mixed with rubber on a mill and the mixture made into a thincement, layers 01!. It seems to be an alkylated phenol (rubber being thealkylating agent) since it is not possible to remove the phenol from themilled product (indicatin that the phenol molecule has chemicallycombined with the rubber molecule). Presumably a combination has takenplace at what was an unsaturated carbon atom in the rubber used as astarting material.

The preparation of the iratol is described in U. S. A. Patent 2,158,530(Williams), and in the interest of brevity reference is made thereto fordetails. As pointed out by the patentee, iratol is resinous,thermoplastic, benzene soluble, contains 1% to 5% of the phenolchemically combined with the rubber, is resistant to acids and alkalies,does not adhere to rubber, has an impact strength similar to phenolaldehyde resins, imparts a hardness to rubber (when compoundedtherewith) like glue and Montan wax, and can be hydrogenated attemperatures in the range 80-200 C. in the presence of an acidiccatalyst.

For convenience it may be pointed out that the amount of phenolicmaterial (phenol, naphthol, etc.) may vary widely. It is sometimespreferable to use an excess of the phenolic material, that is, more thanwill chemically combine with the rubber, and although such a reactionproduct may be employed, it is preferred that the uncombined excess beremoved, for example, by abstraction from the phenol derivative of therubber. Ordinary extraction procedures utilizing such materials asalcohol solvents, such as ethanol and butanol, are suitable for thispurpose. The reaction product may also be purified by dissolving intoluene and precipitating the reaction product with ethyl alcohol (whichretains the uncombined phenolic body in solution). The materials used inthe specific examples were treated to remove the uncombined phenol.

Generally the products prepared by milling 5 to 20 parts of betanaphthol with 100 parts of rubber in the presence of 4 parts sulfuricacid as a catalyst, are preferred. Although this type of material wasemployed in the spec fi examples, it is to be understood that any one ora plurality of the products disclosed in said patent may be emplayedwhen desired.

Various phenols in addition to the beta naphthol of the examples, forinstance, hydroxy benzene, chlorophenol, cresol and dihydroxy-diphenyl,may be employed in the manufacture of the iratol. One or more phenolicmaterials may be used in carrying out the reaction. Catalysts other thanthe sulfuric acid, for example, dihydroxy-fluoro-boric acid. organicsulfonic acids, hydroxy-iluoro-boric acid, and boron trifluoride, may beemployed.

The term iratol applies only to the type of material obtained accordingto the aforementioned U. S. A. Patent 2,158,530 and is not to beconstrued broadly enough to cover isomers or 7 like derivatives ofrubber which might be obtained by using phenol or phenol sulfonic acidin a simple catalytic capacity.

As the moistureproofing agent, any wax (used generically to include waxyor wax-like sub- 8 stances like paraffin wax, as well as true waxeswhich are monohydric alcohol esters of higher fatty acids) or mixture ofwaxes, may be employed. Ordinarily parafiln wax melting above 50 C., orbetter, that melting at 60 C. (and above) is preferred.

The new cementing agent compositions are especially useful in coatingcompositions applied to transparent, smooth, substantially non-porous,non-fibrous sheet, such as those composed of cellulosic material. forexample, regenerated cellulose, ethyl cellulose and cellulose acetate;albuminous material, for example, gelatin and casein; and polyvinylcompounds, for example, polyvinyl alcohols and polyvinyl acetals. Watersensitive sheet obtained by coagulation or precipitation and/orregeneration from aqueous (or aqueous alkaline, for example, alkalimetal hydroxide and the like) dispersions (or solutions), for example,viscose, cuprammonium and like regenerated cellulose, polyvinyl alcohol,low-(lowly) substituted (less than one mol per glucose unit) celluloseethers (U. S. A. Patent 2,123,880 to Ellsworth), such as glycolcellulose, cellulose glycolic acid, alkyl (methyl, ethyl, etc.)cellulose, and the like, are especially satisfactorily coated with themoistureprooflng compositions of this invention.

As indicated above, the presence or the new iratol combinations orcompositions also improves coating compositions used on organic solventsoluble compounds like cellulose ethers, for example, ethyl cellulose,and cellulose esters, for example, cellulose acetate. The same is truewith paper, modified paper, lowly esterified cellulose, etc.

The new compounds can also be used to coat fabrics, to prepare moldingmaterials, to act as cementing (binding) agents in protective coatingsfor wood, metal, etc., as adhesives, and for numerous other purposes.These compositions also serve admirably as adhesives in the laminationof sheet material, for example, regenerated cellulose, cellulosederivatives of the same or difi'erent kinds, regenerated cellulose topaper, etc. especially when a moistureprooi' product is desired.

The diamino diphenyl methanes and benzhydrols may be introduced into theiratol or compositions containing the same, in any desired manner.Ordinarily the incorporation is made by the use of a mutual solvent orby milling, but grinding, kneading, and other conventional mixingprocedures are satisfactory.

The stabilizing effect of the diamino diphenyl methanes and likeadditive materials is roughly proportional to the amount used in or withthe iratol. The practical limits are from 0.03 to 0.5 per part (3%50%)of iratol. Improvement obtained by using amounts below theaforementioned lower limit is detectable but not great enough to be ofpractical value, and no advantage seems to be afforded by usingproportions greater than the aforementioned upper limit. Preferably 3%to 15% is employed.

In the preferred procedures, moistureproofing coatings are applied bypassing the base sheet through a bath (solution) containing the coatingcomposition but spraying a corresponding solution on the base sheet, andthe other schemes known to the art, particularly that listed elsewhereherein, can be used satisfactorily.

The properties of the new iratol compositions may be enhanced andmodified in known ways, by the incorporation of minor proportions ofother materials. Details of the conventional modifying practices such asdyeing, pigmenting, plasticizing (or softening), transparentizing, andlike procedures and materials used therein, are well known and aredisclosed in the patents listed elsewhere herein. Reference is madethereto for specific details. Beneficial results are frequently broughtabout by incorporating natural and/or synthetic resins.

Moistureproofness, moistureprooflng and moisture-proof materials andexpressions are defined in U, S. A. Patent 2,147,180 (Ubben). In theinterest of brevity the definitions are not repeated here. The terms andexpressions related thereto and employed herein are used in accordancewith such definitions.

Heat seal bond and heat seal bond strength are defined and a standardtest for their determination is given in U. S. A. Patent No. 2,147,180(Ubben). In the interest of brevity the definitions are not repeatedhere. The terms and expressions related thereto and employed herein areused in accordance with such definitions and description.

Many of the advantages of the present invention are believed apparentfrom the foregoing part of the specification. The compositionscontaining iratol, and the iratol itself, are stabilized for longperiods of time, extending the useful life many times over, even underconditions involving high temperatures and/or strong light.

The iratol-diamino diphenyl methane cementlng agent material makes itpossible to produce moisture-proof products which retain their desirableproperties (heat seal, color, etc.) over an unexpectedly long period oftime.

As many apparently widely different embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that this invention is not limited to the specificembodiments thereof except as defined in the appended claims.

I claim:

1. An article of manufacture comprising a base formed of a sheet offlexible, non-moistureprcoi', non-fibrous and transparent materialcoated with a moistureprooflng composition comprising a film-formingsubstance and a moistureproofing wax in proportions and of a thicknessto produce a transparent moisture-proof product, said film-formingsubstance being a reaction 10 product of rubber and a phenol containing1% to 5% of the phenol chemically combined with the rubber, which isresinous, thermoplastic, benzene soluble, acid resistant, alkaliresistant, which does not adhere to rubber, which has an impact strengthsimilar to phenol aldehyde resins, and which imparts a hardness torubber, like glue, said film-forming substance having incorporatedtherein from 0.5% to 50% (based on the filmfcrming substance) of acompound having the formula H H-(CHg) 1-NO i ON(CH=)H l 1 (h m. H 1/methane.

JAMES A. MITCHELL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 0 1,787,064 Calcott et al Dec.30, 1930 1,954,377 Calcott et al Apr. 10, 1934 2,158,530 Williams May16, 1939 2,203,597 Morse et al June 4, 1940 2,209,965 F'inzel Aug. 5,1940 2,233,576 Balon Mar. 4, 1941 2,230,359 McKenzie Feb. 4, 19412,306,487 Mitchell Dec. 29, 1942 2,321,764 Mitchell June 15, 1943Certificate of Correction Patent No. 2,430,726.

November 11, 1947.

JAMES A. MITCHELL It is hereby certified that error appears in therinted specification of the above numbered patent requiri "methyl-4:read methylthis correction therein that the Patent Oflice.

correction as follows:

4 and that the said Letters Patent shoul same may conform to the recordof the case in the olumn 10, line 25 claim 2, for d be read with S gnedand sealed this 20th day of January, A. D. 1948.

THOMAS F. MURPHY,

Assistant Oommiuimr of Patents.

ticizing (or softening), transparentizing, and like procedures andmaterials used therein, are well known and are disclosed in the patentslisted elsewhere herein. Reference is made thereto for specific details.Beneficial results are frequently brought about by incorporating naturaland/or synthetic resins.

Moistureproofness, moistureprooflng and moisture-proof materials andexpressions are defined in U, S. A. Patent 2,147,180 (Ubben). In theinterest of brevity the definitions are not repeated here. The terms andexpressions related thereto and employed herein are used in accordancewith such definitions.

Heat seal bond and heat seal bond strength are defined and a standardtest for their determination is given in U. S. A. Patent No. 2,147,180(Ubben). In the interest of brevity the definitions are not repeatedhere. The terms and expressions related thereto and employed herein areused in accordance with such definitions and description.

Many of the advantages of the present invention are believed apparentfrom the foregoing part of the specification. The compositionscontaining iratol, and the iratol itself, are stabilized for longperiods of time, extending the useful life many times over, even underconditions involving high temperatures and/or strong light.

The iratol-diamino diphenyl methane cementlng agent material makes itpossible to produce moisture-proof products which retain their desirableproperties (heat seal, color, etc.) over an unexpectedly long period oftime.

As many apparently widely different embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that this invention is not limited to the specificembodiments thereof except as defined in the appended claims.

I claim:

1. An article of manufacture comprising a base formed of a sheet offlexible, non-moistureprcoi', non-fibrous and transparent materialcoated with a moistureprooflng composition comprising a film-formingsubstance and a moistureproofing wax in proportions and of a thicknessto produce a transparent moisture-proof product, said film-formingsubstance being a reaction 10 product of rubber and a phenol containing1% to 5% of the phenol chemically combined with the rubber, which isresinous, thermoplastic, benzene soluble, acid resistant, alkaliresistant, which does not adhere to rubber, which has an impact strengthsimilar to phenol aldehyde resins, and which imparts a hardness torubber, like glue, said film-forming substance having incorporatedtherein from 0.5% to 50% (based on the filmfcrming substance) of acompound having the formula H H-(CHg) 1-NO i ON(CH=)H l 1 (h m. H 1/methane.

JAMES A. MITCHELL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 0 1,787,064 Calcott et al Dec.30, 1930 1,954,377 Calcott et al Apr. 10, 1934 2,158,530 Williams May16, 1939 2,203,597 Morse et al June 4, 1940 2,209,965 F'inzel Aug. 5,1940 2,233,576 Balon Mar. 4, 1941 2,230,359 McKenzie Feb. 4, 19412,306,487 Mitchell Dec. 29, 1942 2,321,764 Mitchell June 15, 1943Certificate of Correction Patent No. 2,430,726.

November 11, 1947.

JAMES A. MITCHELL It is hereby certified that error appears in therinted specification of the above numbered patent requiri "methyl-4:read methylthis correction therein that the Patent Oflice.

correction as follows:

4 and that the said Letters Patent shoul same may conform to the recordof the case in the olumn 10, line 25 claim 2, for d be read with S gnedand sealed this 20th day of January, A. D. 1948.

THOMAS F. MURPHY,

Assistant Oommiuimr of Patents.

